"Knockdown" assemblies used for sign construction in the advertising and sign display business involving prefabricated signboards for assembly with sign posts are invariably complex in construction, expensive to manufacture and hard to assemble. They have tended to lack structural stability after a time after installation due to dependence upon tightness and fit of the many fasteners used in their construction which have a tendency to work loose. This requires much maintenance.
There is an established need in the advertising and sign display business for a prefabricated sign construction which has a minimum of fasteners and a self-locking capability for "buttoning-up" the sign upon final asssembly which is not sensitive to looseness of fit.